by Evan the Unrelentless

May 14, 2011

Recoating A Giant Mirror

In the Chilean desert is an aluminum floor that holds the heavens like a modern equivalent of the Sistine Chapel's ceiling. Does this fellow feel a connection to the painter Michelangelo or does he realize that he is Michelangelo's opposite, their circumstances opposed in nearly every way, starting with their physical orientation but also in their media,garb, their theology, the reason for their work, their support teams.

How beautiful his mirror is, the ESO mirror of the European Space Agency. Considered as an art object, a flawless reflective polished disc is on par with this, this, and this.

Perhaps this (unnamed) mirror technician in the clean suit is to Michelangelo as Philip Glass is to JS Bach, a secularist modern portrayer of beauty, and of heaven (the substance, if not the meaning).

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The following images are all from Video #15 from the European Space Telescope.

The episode is all about cleaning the the enormous telescope's 10 meter aluminum mirror. (ESOCast link , 10 minute video) Because the telescope is completely unporotected, the mirror becomes dirty. To keep the optics really ultra perfect they remanufacture the whole mirror periodically, keeping the ceramic form but dissolving the reflective part off with acid and washing it all away. I actually find these day-in-the-life stories of these Chilean desert scientists to be as exotic as the actual science that they're discovering with their telescope.

which means the solid aluminum is turned into a dissolved salt and can be flushed away. (I'm assuming they're using hydrochloric acid but it's the same with sulfuric acid, nitric acid, I think.)

The host of the show points out that since the mirror only needs a few million atoms thick coating, 18 grams of Aluminum is enough to cover the whole thing. They put it on with ion-sputtering in a (huge) vacuum chamber. I know that computer companies are pretty excited if they can get silicon wafers that are even 24 inches to sputter a microprocessor patttern accurately, so it's interesting that sputtering works for this much larger (albeit undetailed) object.

Here's the team. Almost three dozen people willing to live in the desert and pull the mirrors out of each telescope every 18 months.